Up to 2 million Americans suffer from non-healing lower extremity wounds, accounting for 162, 500 annual hospitalizations, 100,000 major limb amputations and one billion dollars per year in health care costs. These wounds usually result from arterial insufficiency alone, or in combination, with diabetes and standard available therapies carry only 30-40% success. The long-term objective of the proposed work is to identify molecules that induce closure of ischemic wounds by restoring a mature microvasculature. Our overall hypothesis is that the cell-specific overexpression of such molecules within the base of the wound can produce a cytokine milieu that is favorable for restoring neovascularization and skin architecture. These molecules could be potentially delivered to a non-healing wound by harvested bone marrow-derived cellular precursors. Activated endothelial cells for neovascularization of wounds are derived from two separate pools, a pool of resident cells within the adjacent tissue and a pool of precursor cells from the bone marrow. Our working hypothesis is that dysfunctional healing in ischemic wounds may be due to an imbalance between factors derived from stromal cells (e.g. fibroblasts) that stimulate the resident endothelial cells and/or insufficient recruitment, differentiation, or survival of precursor cells from the bone marrow into the wound bed. Specifically, we will (1) determine the role of bone marrow-derived endothelial progenitor cells in neovascularization and healing of ischemic wounds; (2) study the role of fibroblasts and fibroblast-derived growth factors like insulin-like growth factor-1 (IGF-1) and platelet derived growth factor B (PDGF-B) in the activation and capillary disorentiation of bone marrow-derived endothelial cell precursors and the recruitment of these precursors to ischemic wounds. We will use non-diabetic and diabetic murine models with surgically created arteria! insufficiency as they complement each other in mimicking wound healing in patients that tend to develop non-healing ischemic limb wounds. In addition, we will use in vivo human/murine chimeric models and models of human angiogenesis in vitro to add information more specific to human cells.